The mechanisms of action of oligomeric proteins that participate in higher levels of organization will be studied to gain understanding of how they are held together and how they interact with one another. A low resolution model of a transacetylase-flavo-protein subcomplex of the pyruvate dehydrogenase complex has been determined and these results will be extended to better define the flavoprotein binding sites on the core enzyme of this complex. We also propose to continue research in the domain subunit structures of the other core enzymes of alpha-keto acid dehydrogenase complexes and to initiate higher resolution x-ray studies on one of the component enzymes. In addition, the structure of a dimeric invertebrate hemoglobin homodimer should be completed during this next period.